101Leafy researched the games.
Beast Thunderbow

Hard Bow of Black Rajang pelt with a fiery aura. Normal people can't use it.
| Class | Bow |
|---|---|
| Rarity | 10 |
| Attack | 300 |
| Thunder | 110 |
| Slots | 0 |
| Price | 95,000z |
Upgrades
| Upgrades into | BeastKingThunderbow |
|---|
Upgrade tree from モンスターハンターポータブル 2nd G 公式ガイドブック (Enterbrain, 2008), page 802.
Materials
Blk Rajang Pelt+ ×4, Hvy Rajang Fang ×5, Hard Rajang Claw ×3, Gold Rajang Pelt ×2